The invention relates to a semiconductor assembly, in particular to a remote control reception module.
The main components of a semiconductor assembly are a carrier and semiconductor components mounted on this carrier, and in addition a housing that can be designed in the form of a casting.
In semiconductor assemblies with components having a greater overall volume, the carrier is generally a Printed Circuit board (PCB) usually comprising an insulator provided with conducting paths. By contrast, semiconductor assemblies with components having a lower overall volume typically have a metal frame configuration, in which at least one semiconductor component is attached to conducting strips, which include a ground strip segment. The housing in the case of the strip configuration generally takes the form of a casting. A semiconductor assembly with metal frame configuration therefore has the following components:
a ground strip segment for connection to ground, as one of at least two strip segments;
at least one semiconductor component attached to the upper part of the ground strip segment on a carrier section of the ground strip segment; and
a casting enclosing the upper part of the strip segments.
In many semiconductor assemblies, it is necessary to shield at least one of the semiconductor components they contain against electromagnetic interference radiation. This applies in particular for all types of detectors for electromagnetic radiation Semiconductor assemblies with shielding typically have the aforementioned design with a carrier PCB to which the shielding can easily be attached. The shielding comprises, for example, a housing of an electrically conductive plastic, of sheet metal or of a wire grid.
Optical shielding is also necessary. Remote control reception modules, as used in TV sets for example, receive modulated IR radiation emitted by semiconductor diodes, in a wavelength range in which interference radiation sources, for example light bulbs, fluorescent lights or energy-saving bulbs, also emit infrared radiation. A silicon (Si) pin diode that absorbs the radiation up to about 1100 nm is typically used as a detector in the reception module. The interference radiation is filtered out towards the short-wave side by a cutoff filter whose absorption edge is around 800 nm, for example. The absorption edge of the filter can easily be set by selection of suitable coloring. The colorant is generally mixed into the casting material. The filter must be at least in the area between an opening in the electromagnetic shielding and the detector surface. To prevent electromagnetic interference radiation entering this opening in the shielding, various measures are taken. One of these is to seal the opening with an electrically conducting foil that is permeable to the radiation to be received. Another measure is to provide a perforated metal plate or wire grid in the opening. A third measure is to provide the detector with a front contact connected to ground.
The known semiconductor assemblies having at least one semiconductor component to be shielded against electromagnetic radiation require a large amount of space on account of the shielding which must be specially fitted, and are expensive to manufacture. They also require a dependably acting electrical connection between the shielding and a ground connection.
The problem was therefore to provide a semiconductor assembly having at least one semiconductor component to be shielded against electromagnetic radiation, that can be compactly built manufactured inexpensively and that ensures a dependable ground connection of the shielding.